Question

So I have 3 main tables (the data is not important):

• Customer
• Group
• Employee

And a couple of “many-to-many” tables to join the other 3 tables:

• GroupCustomer
• GroupEmployee

In essence, a customer can belong to many groups, and an employee can belong to many groups.

So now lets say I have queried for a specific Customer. So I have something like:

Customer customer1 = GetCustomer1();

Now I want to get a count of distinct employees that are in any group that the customer is also in…

int count = customer1.GroupCustomers.SomeLinqMagicGoesHere

So, what is the Linq magic that I need?

important: The relationships are generated using linq-to-sql

---

Some desired input/output if it help explain my needs:

Customer
--------
C1
C2

GroupCustomer
--------
C1 | G1
C1 | G2
C2 | G1

Group
--------
G1
G2

GroupEmployee
--------
E1 | G1
E1 | G2
E2 | G2

Employee
--------
E1
E2

So the count number I want for C1 should be 2. And the count for C2 should be 1.

Hope that hasn’t confused the issue more!

Answer 1

maybe:

int count = costumer.GroupCustomers
    .SelectMany(gc => gc.Group.GroupEmployees)
    .Select(ge => ge.EmployeeID)
    .Distinct()
    .Count();